Devices for examining the optical properties of surfaces are known from the prior art. Generally, these devices use a light source which directs light at the examination surface and a detector that detects and evaluates the light reflected or diffused off of the surface. Such evaluation allows a determination of the optical properties of surfaces such as color, gloss, orange peel and the like. Such a determination or characterization is required since motor-vehicle bodies or their paintwork make different impressions on the human eye depending on the incident light, thus requiring a neutral characterization for comparing different surfaces.
The devices known from the prior art are placed on the examination surface. In the prior art there is the problem that for example in the case of curved surfaces, measurement results of identical measuring points also depend on the incident angle of the light on the examination surface. Such curvatures may also lead to incorrect results.
This effect may occur for example when examining paint coatings comprising pigments or so-called flakes. These pigments or flakes are for instance metal particles statistically distributed in the layer of paint or on its surface. The pigments exhibit different characteristics in dependence on the incident angle of the light such as a slightly changed angle of observation, a different color or a different brightness. If present, the reflected light is particularly strongly affected by deviations from the angle of reflection.